One arrangement for providing position sensing for systems utilizing large cylinder rods is to form a gear teeth-like profile on the surface of the cylinder rod, which has ferromagnetic base material. A sensor element, typically a Hall Effect sensor, is mounted to a magnet. As the gear tooth profile, formed on the cylinder rod, passes the Hall Effect sensor a pulse is generated as a result of the Hall Effect sensor detecting the presence of the ferromagnetic material. Each pulse is associated with a distance of travel from one gear tooth on the cylinder rod to the next.
To form the gear teeth, grooves between each of the gear teeth must be individually machined about the circumference of the cylinder rod. Increasing the number and the proximity of the grooves increases the resolution of the pulse signal obtained for measuring the position of the cylinder rod. However, machining the grooves is a time consuming and expensive task.
Additionally, the cylinder rod is typically formed of ferromagnetic material, such as steel. Common applications of cylinder rods requiring position sensing include marine and brackish water applications, such as offshore drilling, locks, dams and draw bridges. In order to protect the cylinder rod from corrosion and other damage as a result of these environments, a corrosion resistant, thermal sprayed coating is applied. Typically, a thin bonding layer is applied to the cylinder rod, and the corrosion resistant coating is applied over that forming a mechanical bond with the bonding layer and the cylinder rod. The coating must be applied after all of the gear teeth have been formed, due to the complexity of grinding the grooves to form the gear teeth. Additionally, the two layers of non-magnetic coating reduce the sensors ability to detect the gear teeth. This limits the available thickness of the corrosion resistant coating. However, limited thickness of the corrosion resistant coating reduces the life of the cylinder rods.